Well you can try these tricks to make batter drain less faster :P(and yes the whole pidgeot (Peny) and donkey from Shrek(Olly) problem is probably just a pesky bug ,or the animal instincts got to them:P)
Basically this(this is the fix for your battery draining:):
- Make sure Auto brightness is on or dim the screen.
- Shorten the screen time-out.
- Try out the battery saver mode.
- Use Airplane Mode or no data mode… sometimes.
- Turn off vibrate.
- Delete those apps you never use anymore.